AEKOBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 525 



organisms measure about 3 to 4 microns in length. On glu- 

 cose agar the organisms measure about 0.375 by 2.25 to 3 mi- 

 crons and the ends are rounder but there is no change in the 

 character of the cytoplasm. (Figures 81 and 82.) 



Motility. Active progressive and rotatory motility in 24 hour 

 agar culture. 



Staining properties. Organisms stain readily by the ordinary 

 dyes. Gram-negative. 



Spore formation. Spores are formed early appearing in 24 

 hours on plain agar in the thermostat, somewhat later on glu- 

 cose agar. They are usually formed in the central portion of the 

 rods causing a distinct sweUing so that the bacilli become spindle- 

 shaped. Rarely the spores appear toward the end of the rods 

 in a subterminal position or they may even be terminal. They 

 are much wider than the vegetative rods and when free are dis- 

 tinctly cylindrical with pointed spurs. They measure 0.625 by 

 1.125 to 1.5 microns. By the end of 48 hours both at 37° and 

 at 22° the spores are abundant. 



Agar slant. Thick moist rather dark non-spreading growth in 

 24 hours, becoming thicker and raised in 48 hours and in older 

 cultures. Easily scraped off from medium. 



Agar stab. Growth along hne of inoculation in 24 hours, 

 gradually spreading on the surface of the agar at the point of 

 puncture. 



Agar colonies. Round regular rather translucent colonies in 

 24 hours, granular with smooth margins under the low power. 

 Older colonies show pale central areas with heaped up peripheries 

 but remain small regular and slightly raised, resembling those of 

 Bacillus coli. 



Glucose agar slant. Thick moist cream-yellow non-spreading 

 growth in 24 hours, becoming thick heavy with an irregular 

 surface of a reddish brown color in old cultures. Reaction 

 alkaline. 



Glucose agar colonies. Irregular heaped up colonies in 24 

 hours tending to become slimy or viscid-looking. Under low 

 power they are irregular, heaped up or swollen, with entire mar- 

 gins. At times they have a dew-drop appearance. On old cul- 



